The extinction of the woolly mammoth has long been attributed to human overhunting, but recent evidence suggests that climate change was the primary driver. Three key points support this view. First, the timing of mammoth extinctions across different regions correlates more closely with periods of rapid climate warming than with human arrival. For instance, on Wrangel Island, mammoths survived until about 4,000 years ago, long after humans had arrived, but disappeared shortly after a dramatic shift to wetter, warmer conditions. Second, mammoth populations showed signs of genetic decline before human contact, as indicated by a reduction in genetic diversity in fossils dating to the last interglacial period, when climate was already fluctuating. This suggests that environmental stress, not hunting, weakened the species. Third, mammoths were adapted to cold, dry steppe-tundra habitats. As the climate warmed, these habitats shrank and were replaced by forests and wetlands, which would have reduced available grazing land and disrupted their migratory patterns, leading to starvation and population collapse. Human hunting, while possibly a contributing factor, cannot explain the global pattern of extinction that aligns with climate-driven habitat loss.
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The reading's claim that climate change alone drove woolly mammoth extinction is unconvincing. While climate did play a role, human hunting was the decisive factor. First, the correlation with climate is not as clear as suggested. On Wrangel Island, the mammoths survived through several earlier warm periods, including the Bølling-Allerød warming, but went extinct only after humans arrived on the island. This timing points to human activity, not climate. Second, the genetic decline mentioned in the reading actually supports the overhunting hypothesis. When human hunters target large animals, they reduce population size, which leads to inbreeding and loss of genetic diversity. Thus, the observed genetic decline may be a result of hunting pressure, not a pre-existing vulnerability. Third, the loss of habitat was not as catastrophic as argued. Mammoths were generalist feeders; fossil dung and isotope analyses show they could adapt to a variety of vegetation, including shrubs and grasses in warmer climates. Moreover, human hunting would have been especially devastating because mammoths had slow reproduction rates, making them highly susceptible to even moderate levels of hunting. In sum, climate change alone cannot account for the rapid, island-specific extinctions that coincide with human arrival.
📝 写作提示 Summarize the points made in the lecture, being sure to explain how they cast doubt on the specific points made in the reading passage.
